The Discovery of a Second Field Methane Brown Dwarf from Sloan Digital Sky Survey Commissioning Data

We report the discovery of a second field methane brown dwarf from the commissioning data of the Sloan Digital Sky Survey (SDSS). The object, SDSS J134646.45-003150.4 (hereafter SDSS 1346-00), was selected because of its very red color and stellar appearance. Its spectrum between 0.8 and 2.5 µm is dominated by strong absorption bands of H2O and CH4 and closely mimics those of Gliese 229B and SDSS 162414.37+002915.6 (hereafter SDSS 1624+00), two other known methane brown dwarfs. SDSS 1346-00 is approximately 1.5 mag fainter than Gliese 229B, suggesting that it lies about 11 pc from the Sun. The ratio of flux at 2.1 µm to that at 1.27 µm is larger for SDSS 1346-00 than for Gliese 229B and SDSS 1624+00, which suggests that SDSS 1346-00 has a slightly higher effective temperature than the others. Based on a search area of 130 deg2 and a detection limit of z*=19.8, we estimate a space density of 0.05 pc-3 for methane brown dwarfs with Teff approximately 1000 K in the 40 pc3 volume of our search. This estimate is based on small-sample statistics and should be treated with appropriate caution.

Acidic isoforms of chorionic gonadotrophin in European and Samoan women are associated with hyperemesis gravidarum and may be thyrotrophic

OBJECTIVE

There is conflicting evidence concerning the role of human chorionic gonadotrophin (hCG) in the aetiology of hyperemesis gravidarum (HG); particular isoforms of hCG may be the critical factor. Ethnic differences in HG prevalence and putative thyrotrophic effects of hCG may also relate to differences in hCG isoform profiles. To address these issues we examined the relationship of hCG isoforms to HG and thyroid function tests in two groups of women from ethnic backgrounds with significantly different HG prevalence rates.

PATIENTS AND DESIGN

We enrolled 10 European and 10 Samoan women with HG and an equally sized non-hyperemetic, gestational stage matched control group.

MEASUREMENTS

We administered a questionnaire, generated serum hCG charge-isoform profiles by chromatofocusing and measured the serum concentrations of total hCG, oestradiol (E2), thyrotrophin (TSH) and free thyroxine (FT4).

RESULTS

The mean serum total hCG levels were highest in the Samoan hyperemetics (176,268 IU/l), and overall higher in hyperemetics compared with controls (159,770 IU/l vs. 86,420 IU/l, P < 0.001). When compared with controls, hyperemetics displayed increased hCG concentrations in the more acidic half (pH < 4) of the chromatofocusing pH range (89,843 IU/l vs. 41,146 IU/l, P < 0.003). Serum E2 levels did not differ between the four groups, but correlated with the hCG concentration between pH 5.2 and 4.01. Mean serum TSH levels were significantly lower in hyperemetics than in controls (0.33 mIU/l vs. 1.19 mIU/l, P < 0.001) and correlated with the hCG concentration between pH 4.6 and 2.8, while serum FT4 correlated with the hCG concentration below pH 4.0.

CONCLUSIONS

Acidic isoforms of hCG may play a role in the aetiology of HG and gestational thyrotoxicosis. Minor ethnic differences in hCG isoform profiles were observed, but the relationship of acidic hCG isoforms to HG and serum thyroid hormone levels was largely independent of the patients' ethnicity. The mechanisms by which acidic isoforms might provoke nausea remain uncertain, but do not seem to involve E2, while the longer half-life of acidic hCG isoforms may result in increased in vivo TSH receptor cross-talk with resultant thyrotrophic effects.

A randomized trial of short-term treatment of Graves' disease with high-dose carbimazole plus thyroxine versus low-dose carbimazole

OBJECTIVE

The optimal treatment regimen with thionamide drugs remains a matter for debate. We have investigated whether high doses of carbimazole, when compared with low doses, reduce relapse rates of Graves' disease.

DESIGN

In an open label, randomized, prospective trial of treatment of Graves' disease we compared high doses of carbimazole (6 months of 100 mg carbimazole per day plus thyroxine) to low-dose carbimazole treatment (starting at 25 mg and titrating the carbimazole dose with the aim to maintain serum thyroid function test results within the normal reference range).

PATIENTS

Thirty-seven patients with a first episode of Graves' disease were enrolled.

MEASUREMENTS

During the 6 months of treatment we evaluated the rate of normalization of serum thyroid function tests, changes in serum thyroid auto-antibody levels and the rate of side-effects during treatment. After completion of the 6-month treatment course patients were observed for 2 years for evidence of relapse of Graves' disease.

RESULTS

There were no differences between the two groups either in the rate of normalization of serum thyroid function tests or in serum thyroid auto-antibody levels during treatment. Of the 17 patients randomized to high-dose treatment seven suffered treatment side-effects, compared to only one of the 20 patients receiving low-dose treatment (P < 0.006). There was no significant difference in 2-year post-treatment remission rates on an intention-to-treat basis between the two treatment groups (18.7% vs. 5.9%, P = NS). However, for those patients who completed 6 months of treatment (high-dose group = 9, low-dose group = 16), multivariate survival analysis demonstrated a significantly longer median relapse-free interval (P < 0.04) in the high-dose group (27 weeks; 25th percentile: 9.6 weeks, 75th percentile: 75 weeks) versus the low-dose group (6 weeks; 25th percentile: 4.8 weeks, 75th percentile: 13.1 weeks).

CONCLUSIONS

High-dose carbimazole treatment delays, but does not prevent, relapse from Graves' disease in those patients able to tolerate the treatment. However, it leads to more frequent side-effects than conventional dose treatment.

Treatment of hypothyroidism with once weekly thyroxine

We compared daily T4 therapy with 7 times the normal daily dose administered once weekly in 12 hypothyroid subjects in a randomized cross-over trial. At the end of each treatment we measured serum free T4 (FT4), free T3 (FT3), rT3, and TSH levels and multiple markers of thyroid hormone effects at the tissue level repeatedly for 24 h. Compared with daily administration, the mean serum TSH before the administration of weekly T4 was higher (weekly, 6.61; daily, 3.92 microIU/mL; P < 0.0001), and the mean FT4 (weekly, 0.98; daily, 1.35 ng/dL; P < 0.01) and FT3 (weekly, 208, daily, 242 pg/dL; P < 0.01) were lower. A minimally elevated serum total cholesterol during weekly administration (weekly, 246.8; daily, 232.6 mg/dL; P < 0.03) was the only evidence of hypothyroidism at the tissue level. Compared with daily administration, the mean peak FT4 following weekly administration of T4 was significantly higher (weekly, 2.71; daily, 1.59 ng/dL; P < 0.0001), as was the mean peak FT3 level (weekly, 285; daily, 246 pg/dL; P < 0.01). None of the tissue markers of thyroid hormone effect changed compared to daily T4, and there was no evidence of treatment toxicity, including cardiac toxicity. During weekly T4 administration, autoregulatory mechanisms maintain near-euthyroidism. For complete biochemical euthyroidism a slightly larger dose than 7 times the normal daily dose may be required.

Serum free thyroxine levels in cats maintained on diets relatively high or low in iodine

Excessive or deficient intake of iodine may play a role in the development of goitre and hyperthyroidism in cats. Previous investigations have shown that the serum free thyroxine level of cats is affected by brief administration of food high or low in iodine content. We have now measured serum free thyroxine levels in groups of cats fed relatively high or low iodine diets for much longer periods (5 months). In contrast to our earlier findings, the chronic ingestion of relatively high or low iodine diets did not lead to statistically significant differences in serum free thyroxine levels. The results of the present investigations show that the cat is able to maintain normal levels of thyroid hormone despite prolonged high or low iodine diets. It may be that the adaptive mechanisms that are called into play during chronic high or low iodine intake lead to thyroid disease, particularly in certain predisposed individuals.

Evidence that TGF-beta can inhibit human T-lymphocyte proliferation through paracrine and autocrine mechanisms

Transforming growth factor-beta (TGF-beta) has been documented as having an inhibitory effect on the proliferation and growth of human T-lymphocytes. We examined the relative contribution of both exogenous and endogenous TGF-beta to this inhibitory action. Purified human peripheral blood T-cells were cultured with Con A (0.2 microgram/ml), washed with methyl mannopyranoside, and then cultured in rIL-2 (5 U/ml) with or without TGF-beta (80 pM). Proliferation, as measured by uptake of tritiated thymidine at 72 hr, was inhibited by added active TGF-beta. Addition of neutralizing anti-TGF-beta antibodies at the initiation of culture abrogated the antiproliferative effects of TGF-beta. A mink lung cell bioassay was used to measure endogenous TGF-beta production by the T-cells following transient acidification of the supernatants to activate latent TGF-beta. T-lymphocytes cultured with rIL-2 alone produced low levels of TGF-beta, first detectable at 72 hr. The addition of (active) TGF-beta to these cultures resulted in earlier and higher levels of endogenously produced latent TGF-beta protein. This was reflected at the mRNA level as well. The exogenously added active TGF-beta appeared to be depleted during the culture period, presumably by the activated T-cells, which exhibited elevated levels of types I, II, and III TGF-beta receptors. The increase in TGF-beta protein levels was due to endogenous TGF-beta synthesis and secretion as supported by a capture assay using 35S-labeled culture supernatants. These findings indicate that both paracrine and autocrine mechanisms are involved in the inhibitory effects of TGF-beta on the proliferation of normal human T-lymphocytes and suggest that other TGF-beta-producing cells can augment production of TGF-beta by activated T-lymphocytes.

Hepatocyte membrane injury and bleb formation following low dose comfrey toxicity in rats

Comfrey, a popular herbal remedy, contains hepatotoxic pyrrolizidine alkaloids and has been implicated in recent human toxicity. Although alkaloids from other plant sources have been extensively researched, studies on the hepatotoxic effects of comfrey alkaloids are scant. The effects of high dose comfrey toxicity have been studied and the present investigation was undertaken to identify changes associated with relatively low dose toxicity. Eight young adult rats were dosed weekly for six weeks with 50 mg/kg of comfrey derived alkaloids. The animals were dissected one week after the last dose and the livers examined by light and electron microscopy. Changes at the light microscopic level showed vascular congestion, mild zone 3 necrosis and loss of definition of hepatocyte cellular membranes. Extensive ultrastructural abnormalities were identified in the form of endothelial sloughing and the loss of hepatocyte microvilli. A striking finding was florid bleb formation on the sinusoidal borders of hepatocytes. Many blebs were shed into the space of Disse and extruded to fill, and sometimes occlude, sinusoidal lumina. Platelets were frequently found in areas of bleb formation. There was evidence of late damage in collagenization of Disse's space. Hepatocyte bleb formation is known to occur under a variety of pathological conditions but there is little to no information in the literature on the effects, if any, of bleb formation on fibrogenesis and the microcirculation and its role in the pathogenesis of liver disease. The pyrrolizidine alkaloids of comfrey may serve as an experimental tool to study the process of bleb formation and the intimate relationship between hepatocyte and sinusoidal injury in the liver.

Transforming growth factor-beta inhibits human T-cell proliferation through multiple targets

This study investigates further the inhibitory effects of transforming growth factor-beta (TGF-beta) on human T-lymphocyte responses to mitogenic stimulation. T cells were stimulated either with mitogenic concentrations of PHA or with submitogenic concentrations of Con A followed by the addition of IL-2. DNA synthesis ([3H]thymidine incorporation) in both systems was inhibited by 60-69% in the presence of TGF-beta, with maximal reduction occurring on days 4 and 5 of culture. Cell surface expression of transferrin receptor (TfR) and IL-2 receptor-alpha (p55) were inhibited by 20-80% in the Con A/rIL-2 system and 20-45% in the PHA system in the presence of TGF-beta. In addition, mitogen-induced up-regulation of TfR and IL-2R mRNA levels were inhibited by TGF-beta. Finally, we investigated the effect of TGF-beta on the assembly of clathrin monomers into assembled coated pits and vesicles, and essential step in TfR and IL-2R alpha turnover. Stimulation of T cells using either mitogen system resulted in an increase in the level of assembled clathrin, which was almost completely inhibited by TGF-beta. These findings suggest that TGF-beta may act at several sites in mitogen-mediated proliferative pathways to contribute to the inhibition of T-cell proliferation.

Serum free thyroxine levels respond inversely to changes in levels of dietary iodine in the domestic cat

Because of a perceived increase in the incidence of toxic multinodular goitres in cats in recent years, we investigated the iodine content of three varieties of commercial canned cat foods and studied the acute effects of 'ingestion of these preparations on urinary iodine excretion and serum free thyroxine levels in young, healthy cats. Ten castrated male cats were fed from a common source. The type of food was changed every 2 weeks. Urine and blood specimens were obtained weekly. Serum free thyroxine levels were determined and iodine concentrations in urine were assayed. The iodine content of the cats' food was also assayed. Food varieties of high, intermediate and low iodine content were fed for 2-week periods. There was a consistent, reciprocal relationship between the mean urinary iodine concentration and the mean serum free thyroxine level for each 2-week period. The difference in the mean serum free thyroxine concentrations for the high and low iodine intake periods was highly significant (p<0.01). When the serum free thyroxine level and the urinary iodine level for each cat at each collection throughout the 12-week study were analysed (66 paired results), a strong inverse correlation (r=0.59, p<0.01) was found. We concluded that the serum free thyroxine level in cats, as measured by a kit designed for human serum, is acutely responsive to changes in iodine intake.

Iodine content of commercially-prepared cat foods

Twenty-eight varieties of commercially-available cat food (23 canned, 5 dried) were analysed for iodine. The iodine concentration varied from less than 0.37 micromol/kg to 41.8 pmol/kg, wet weight (less than 1.48 micromol/kg to 167 micromol/kg, dry weight). Excessive or insufficient iodine intake or wide swings in iodine intake over prolonged periods may contribute to thyroid disorders in cats.

Serum levels of free and bound testosterone in hyperthyroidism

OBJECTIVE

The aim of this study was to improve knowledge about the relationships between free and bound forms of testosterone in serum and the major testosterone-binding proteins during hyperthyroidism.

DESIGN

Nine men and 11 women were studied when hyperthyroid due to Graves' disease and again after at least 3 months of euthyroidism.

MEASUREMENTS

The serum concentrations of free T3, free T4, TSH, sex hormone-binding globulin (SHBG), LH, progesterone and free, non-SHBG bound and total testosterone were determined.

RESULTS

For both sexes, hyperthyroidism was associated with significant elevations of the mean total testosterone and sex hormone-binding globulin (SHBG) levels and significant depressions of the mean percentage and concentration of non-SHBG-bound testosterone and the mean percentage of free testosterone. For women, the mean free testosterone concentration was significantly lower during hyperthyroidism than during euthyroidism; no significant difference in mean free testosterone concentration was observed between hyperthyroid and euthyroid men. When the experimentally derived data were analysed according to a model based on the binding constants of testosterone with SHBG and albumin, the simulated results for each patient when hyperthyroid and euthyroid paralleled the actual results. However, the model consistently overestimated the actual amounts of non-SHBG-bound testosterone. There was a significant correlation between SHBG concentration and the severity of thyrotoxicosis as measured by the change in thyroid hormone levels between euthyroidism and hyperthyroidism.

CONCLUSIONS

Our results support the following pathogenetic sequence: thyrotoxicosis leads to a rise in serum SHBG concentration which is accompanied by an increase in testosterone concentration, a fall in the concentration of non-SHBG-bound testosterone and little or no change in the concentration of free testosterone.

The management of Graves' disease in New Zealand: results of a national survey

OBJECT

to compare treatment of Graves' disease in New Zealand with treatment in Europe and the United States of America (USA).

METHODS

we circulated a questionnaire used in recent surveys in Europe and USA to all specialist physicians in New Zealand registered with the Medical Council. In the questionnaire a patient with uncomplicated Graves' disease was given as an index case, followed by eight clinical variations with regard to goitre size, severity, sex, age and previous treatment.

RESULTS

two hundred and ninety-six (79%) out of 374 physicians responded to a preliminary letter asking whether they would be willing to participate in the survey. Of the respondents 71 (24%) saw more than two patients with Graves' disease per year and were included in the analysis (186 saw fewer than two cases per year and 39 failed to return questionnaires). For the index case, 55% of New Zealand respondents would treat with antithyroid drugs, 41% with radioiodine and 4% with surgery. For the index case and its variations the use of radioactive iodine by New Zealand physicians was greater than their European, but less than their American, counterparts. Surgery was infrequently recommended in any of the countries except for the patient with a large goitre, for whom 24% of New Zealand and 51% of European respondents would recommend subtotal thyroidectomy.

CONCLUSION

we have demonstrated a spectrum of behaviour by physicians in the treatment of Graves' disease based on infrequent use of surgery and the willingness to use radioactive iodine instead of treatment with antithyroid drugs. New Zealand physicians appear to be more conservative in the use of radioiodine than their American, but less than their European counterparts.

Once daily, low dose, short term antithyroid drug treatment of Graves' disease is followed by an unacceptably high relapse rate

Thirty-six patients with hyperthyroid Graves' disease were treated with low doses of antithyroid drugs until thyroid function test results indicated euthyroidism or mild hypothyroidism (median treatment period three months, range 1.5-8 months). Less than one-half (42%) of the patients remained hyperthyroid after two months of treatment, but 21% were still thyrotoxic after three months of treatment. Of 32 patients who completed treatment and entered the observation period after treatment was withdrawn, 27 (84%) have relapsed, two have remitted for one year or more and three have been followed for less than one year without relapse. Although once daily, low dose, short term antithyroid drug treatment of patients with Graves' disease in the Wellington area satisfactorily controls the hyperthyroidism in the majority of cases, it is followed by an unacceptably high relapse rate.

Iodine intake and the seasonal incidence of thyrotoxicosis in New Zealand

We explored a possible relationship between the seasonal variation in the incidence of thyrotoxicosis in our area and iodine intake, as assessed by measuring the 24-h urinary iodide excretion rate eight times at 3-month intervals in a group of normal subjects and in 992 outpatient specimens over a 2-year period (1988-1990). For the period 1978-1990, 139 cases of thyrotoxicosis were diagnosed during the warmer half of the year (November-April) and 100 cases during the cooler half (May-October). This difference was statistically highly significant (P = 0.013). A similar disproportionality in the incidence of thyrotoxicosis was observed between the warmer (57%) and cooler (43%) halves of the year for the period 1988-1990. During the 1988-1990 period there was no discernible seasonal variation in either the milk iodide concentration or in the cumulative mean 24-h urinary iodide excretion rates for the normal subjects or the outpatients. We conclude that the higher proportion of thyrotoxic patients diagnosed during the warmer 6-month period of the year in our area is best explained by the fact that symptoms tend to be less tolerable in warm weather. A comparison of our findings on 24-h urinary iodide excretion rates with data collected in our area 25 years ago suggested that iodine intake may have declined.

A survey of the iodide concentration of human milk

The iodide concentration of human milk from mothers living in the Wellington area and of six prepared infant formulae was measured. A total of 93 human milk samples were assayed, 14 from mothers of infants delivered at less than 35 weeks gestation and collected within 30 days of delivery (group A), 57 samples from mothers of infants delivered at 35 or more weeks gestation and collected within 60 days of delivery (group B) and 22 samples from mothers with infants aged greater than 60 days (group C). There was no significant (p greater than 0.05) difference between the means (SE) of groups A 1.14 mumol/L (0.20) and B 0.98 mumol/L (0.07). The mean for group C 0.39 mumol/L (0.03) was significantly less (p less than 0.05) than the means for both groups A and B. For groups A, B and C combined, there was a correlation (r = 0.44, p less than 0.01) between the milk iodide concentration and the iodide/creatinine ratio of a maternal urine specimen obtained immediately before or after the milk specimen. Formula milk preparations based on cow's milk contained higher concentrations of iodide than human milk.

Haemostasis in hypothyroidism

Abnormalities that have been reported for platelet indices and function, coagulation factors and tests, and the fibrinolytic system in hypothyroidism are reviewed. These abnormalities, although usually of limited importance clinically, may occasionally lead to major bleeding episodes and to diagnostic confusion.

Disturbances of calcium and magnesium metabolism occur in most hyperthyroid patients

The concentrations in serum of total and ionised calcium, phosphate, magnesium, albumin and alkaline phosphatase activity were measured in patients when hyperthyroid and again when euthyroid. Significant declines in the mean values of ionised calcium, phosphate and alkaline phosphatase activity and significant increases in the mean concentrations of magnesium and albumin were observed. Similar changes were observed in most individual patients. Levels of ionised calcium greater than two standard deviations (representing between batch imprecision) above the upper limit of the reference range were present in 15.6% of hyperthyroid patients. The hyperthyroid levels of calcium, ionised calcium and alkaline phosphatase activity were highest in patients with the most severe thyrotoxicosis. Disturbances of calcium and magnesium metabolism are frequent in hyperthyroid patients.

Serum and red cell folate and serum vitamin B12 levels in hyperthyroidism

Serum and red blood cell folate levels and serum B12 concentration were determined by radioassay in 20 hyperthyroid patients and compared with values obtained when the same patients had been euthyroid for at least 4 months. In hyperthyroidism, the levels of serum and red blood cell folate were significantly (P less than .01) higher than when euthyroidism was achieved. There was no significant change in serum B12 concentration. Declines in serum and red blood cell folate levels between hyperthyroidism and euthyroidism occurred in 15 and 16 of the 20 patients, respectively. Although the explanation for the relative elevations of serum and red blood cell folate levels in hyperthyroid patients is unclear at present, our findings do not support the view that hyperthyroidism in man is associated with depletion of folate stores or subclinical deficiency of the vitamin.

Renal function and electrolyte levels in hyperthyroidism: urinary protein excretion and the plasma concentrations of urea, creatinine, uric acid, hydrogen ion and electrolytes

In order to help clarify the effects of hyperthyroidism on renal function and electrolyte metabolism, we measured the venous plasma concentrations of urea, creatinine, urate, hydrogen ion and electrolytes, and the urinary concentrations of total protein, albumin, retinol-binding protein, N-acetyl-beta-D-glucosaminidase activity, and creatinine in patients when hyperthyroid and again after they had been euthyroid for at least 4 months. Significant (P less than 0.05) decreases in the mean plasma concentrations of urate and chloride and significant increases in creatinine, total CO2 and hydrogen ion mean concentrations were observed when the patients became euthyroid. The mean concentrations of sodium, potassium and urea did not change significantly. The values of the ratios total protein/creatinine, albumin/creatinine, N-acetylglucosaminidase/creatinine and retinol-binding protein/creatinine were all significantly (P less than 0.05) elevated in random urine specimens obtained from hyperthyroid patients as compared to the values when euthyroid. Mild proteinuria occurs in most thyrotoxic patients which does not appear to be due predominantly to either glomerular or tubular renal injury. The changes in plasma analytes that were observed may be attributed to increases in glomerular filtration rate and tissue nucleic acid turnover and a tendency to respiratory alkalosis in the hyperthyroid patients.

Human placental cytotrophoblast cells: identification and culture

Methods of disaggregation of human placental tissue were assessed with the aim of maximising the yield of cytotrophoblast cells and minimising contamination with other cell types. Brief exposure to crude trypsin was found to be the best way to balance yield of trophoblast cells against contamination by cells of the villous core. Much higher yields of all cell types could be obtained by digestion with other enzymes. Staining for NADH diaphorase activity coupled with general morphology was found to be a reasonably specific, rapid and simple method of distinguishing cytotrophoblast cells in disaggregated mixtures. Alkaline phosphatase activity was an unreliable marker of trophoblast tissue in early placentas, and of the putative cytotrophoblast cells in mixtures of disaggregated cells. Cultures of cells obtained from term placentas were fairly homogeneous, whereas placentas of 6-12 weeks gestation gave heterogeneous cell cultures which became overgrown with fibroblasts.

A search for protein abnormalities in erythrocyte membranes and platelets from patients with multiple sclerosis using double-label two-dimensional electrophoresis

Proteins from erythrocyte membranes and whole platelets from patients with definite multiple sclerosis (MS) and normal subjects were compared using a double-label two-dimensional procedure. No consistent differences were found in the proteins adherent or intrinsic to erythrocyte membranes. The results of initial studies with platelets showed the absence of a group of three protein spots in the electrophoretic gels of the MS specimens. Further experiments suggested that these results were probably due to minor differences in the handling of the MS and normal specimens although the possibility of a difference in protease activity was not completely eliminated.

5'-Nucleotidase of human placental trophoblastic microvilli possesses cobalt-stimulated FAD pyrophosphatase activity

An enzyme with FAD pyrophosphatase activity was extracted from human placental syncytiotrophoblast microvilli and purified to near-homogeneity. The enzyme has been identified as 5'-nucleotidase by several criteria. Throughout purification, parallel increases in the specific activities of FAD pyrophosphatase and AMP phosphatase were observed. The enzyme was a glycoprotein with a subunit molecular weight of 74,000. EDTA treatment resulted in a marked decline in both activities, and restoration of FAD pyrophosphatase activity but not 5'-nucleotidase activity was accomplished by the addition of Co2+ or, to a lesser extent, Mn2+. The substrate specificity of the 5'-nucleotidase activity that we observed agreed closely with the results of others. The pyrophosphatase activity was relatively specific for FAD. ADP, ATP, NAD(H), and FMN were not hydrolyzed, and ADP strongly inhibited both activities. For FAD pyrophosphatase activity, a Km of 1.2 x 10(-5) M and a Vmax of 1.1 mumol/min/mg protein were determined in assays performed in the presence of Co2+. In the absence of added Co2+, the Vmax declined but the Km was unchanged. For 5'-nucleotidase (AMP as substrate) the Km was 4.1 x 10(-5) M and the Vmax 109 mumol/min/mg protein. Hydrolysis of FMN to riboflavin was observed in partially purified detergent extracts of microvilli that contained alkaline phosphatase activity and lacked FAD pyrophosphatase and 5'-nucleotidase activity. The presence of both FAD pyrophosphatase and FMN phosphatase activities in syncytiotrophoblast microvilli supports the view that the placental uptake of vitamin B2 involves the hydrolysis of FAD and FMN to riboflavin which is then absorbed, a sequence postulated for intestinal absorption and liver uptake.

The haematology of hyperthyroidism: abnormalities of erythrocytes, leucocytes, thrombocytes and haemostasis

The abnormalities of erythrocytes, leucocytes, thrombocytes and coagulation that have been reported, particularly in more recent years, to be associated with hyperthyroidism are surveyed. Several areas are highlighted where further investigations could lead to clinically useful insights, improved information about the haematological processes involved or to a better understanding of thyroid hormone action.

A double-label two-dimensional procedure for the analysis of membrane proteins

A previously described double-label two-dimensional electrophoresis procedure (Wheeler et al., Anal. Biochem. 1986 159, 1-7) for the analysis of differences between two complex mixtures of soluble proteins has been modified to allow analysis of proteins requiring detergent for aqueous solubility. The samples are first disrupted by sonication and the insoluble proteins concentrated by high-speed centrifugation. The proteins are then solubilized with sodium dodecyl sulfate and further concentrated in a centrifugal concentrator to achieve protein mixtures suitable for labeling with 14C and 3H by reductive methylation and subsequent two-dimensional electrophoresis. The sample concentration step is quick, minimizes the concentration of sodium dodecyl sulfate in the final sample, and avoids the potential difficulties associated with lyophilization or precipitation. The modified procedure was applied to the analysis of erythrocyte membranes, platelets and isolated placental microvilli. The high resolving power of two-dimensional gel electrophoresis is retained and the procedure is sensitive because the conditions of labeling allow substantial incorporation of radioactivity into protein despite the presence of detergent.

High-affinity binding of riboflavin and FAD by immunoglobulins from normal human serum

The binding of [3H]FAD and [3H]riboflavin to a pooled, human plasma immunoglobulin fraction was studied. For each flavin, the data fit best a model with two binding sites of high affinity and a class of sites of lower affinity. The dissociation constants estimated for the two high affinity sites were 1.73 nM and 0.078 nM for [3H]FAD and 2.43 nM and 0.068 nM for [3H]riboflavin. The results of studies with a series of possible competitors suggested that the flavin ring system was an important determinant of the binding. Other studies showed that the binding reaction was largely enthalpy-driven. Our findings show that normal human immunoglobulins contain one or more species that bind riboflavin and FAD with very high affinity.

Mean platelet volume is increased in hyperthyroidism

In 28 unselected patients with hyperthyroidism, platelet count, platelet hematocrit, mean platelet volume, and platelet distribution width were measured at the time of presentation and again when the patients were euthyroid. On return to the euthyroid state, there were highly significant falls in the mean values of the mean platelet volume (16% decline, P less than 0.001) and the platelet hematocrit (16% decline, P less than 0.001) and a slight but highly significant increase in the mean value of the platelet distribution width (2% increase, P less than 0.01). A decline in mean platelet volume was observed in 24 of 28 patients (86%); three patients showed no change. There was no significant change in the mean value of the platelet count. The observed effects of thyrotoxicosis on platelets appeared to be largely independent of the well-known effects on erythrocytes and white blood cells. An increase in mean platelet volume is a regular feature of hyperthyroidism that has not previously been described.

Seasonality of thyrotoxicosis in Wellington

The month of diagnosis of hyperthyroidism in 183 patients from the area of Wellington, for the period 1977-1986 was ascertained. A significantly greater proportion of cases (58%, p less than 0.05) were diagnosed in the warmer period of the year (November to April) than in the cooler period (May to October). Although seasonal environmental factors, such as changes in iodine intake; or other unrecognised factors, such as differences among the patients themselves, may possibly play an aetiological or pathogenetic role, the significantly greater proportion of thyrotoxic patients diagnosed during the warmer 6-month period of the year is presently best explained by the fact that symptoms tend to be less tolerable in warm weather.

Search for abnormal proteins in erythrocytes and plasma from patients with a major depressive episode

A sensitive double-label two dimensional gel electrophoresis procedure has been used to search for abnormal proteins in plasma and erythrocyte plasma membranes from patients with major depressive illness. For both plasma and erythrocytes, minor qualitative and quantitative differences between the proteins in pooled samples from depressed and normal subjects were observed; however, these were shown to be artifacts and no consistent differences were found.

Multiple sclerosis: a survey of alternative hypotheses concerning aetiology, pathogenesis and predisposing factors

There is abundant evidence that both environmental and genetic factors play a role in the aetiology and pathogenesis of multiple sclerosis. Currently, a virus infection and an abnormality of T-cell function are favoured candidates for the environmental and genetic factors, respectively. However, as long as convincing evidence for a specific viral infection and for a pathogenetic role for T-cells in multiple sclerosis is lacking, it may be worthwhile to consider alternative hypotheses that have been proposed in recent years. These have been classified in this review under the headings Toxins, Dietary and Metabolic Abnormalities, Embolism, Infection, and Immunological Mechanisms.

Hemoglobin A1 and serum fructosamine levels in hyperthyroidism

The severity, prevalence and pathogenesis of abnormalities of carbohydrate metabolism in hyperthyroidism are incompletely defined. The extent of glycosylation of proteins provides an objective, retrospective index of glycemic control. We have measured the percent hemoglobin A1, random plasma glucose level and serum concentrations of fructosamine, total protein and albumin in hyperthyroid and euthyroid subjects attending a hospital-based thyroid clinic. A significant (p = 0.002) increase in the mean value for hemoglobin A1 and a significant (p = 0.0003) decrease in the mean values for fructosamine were found in the hyperthyroid group. The lower mean fructosamine value in the hyperthyroid group was attributed to a concomitant decline in the mean albumin concentration (p = 0.001). The mean value for glucose tended to be higher in the hyperthyroid group, but the difference did not reach significance at the 0.05 level (p = 0.09). The finding of a higher mean hemoglobin A1 concentration in hyperthyroid patients compared to euthyroid subjects is new evidence for a persistent abnormality in glycemic regulation in most thyrotoxic patients.

Double-label two-dimensional electrophoresis of serum and plasma proteins from patients with multiple sclerosis

A double-label two-dimensional electrophoretic procedure has been used to search for abnormal proteins in the serum and plasma of patients with definite multiple sclerosis. The procedure possesses high resolving power and is particularly valuable in comparative studies of complex mixtures of proteins since differences due to gel-to-gel variations in protein mobilities are eliminated. Proteins present in serum and plasma at a concentration of 5-10 micrograms/ml are detected routinely. No consistent differences were observed between patients with multiple sclerosis and normal subjects in comparisons using pooled or individual specimens of serum or plasma. The absence of consistent differences in serum and plasma proteins between normal subjects and MS patients applied even when the sensitivity of the procedure was increased several-fold and when the possibly obscuring effect of albumin in the electrophoretic gels was eliminated. To our knowledge, this study combines the most extensive and sensitive search for consistent abnormalities in serum and plasma proteins in multiple sclerosis sera thus far reported.

A double-label two-dimensional gel electrophoresis procedure specifically designed for serum or plasma protein analysis

A double-label two-dimensional electrophoresis procedure has been developed which is specifically designed for the comparison of serum or plasma proteins in two different samples. Proteins are labeled by reductive methylation with [14C]- or [3H] formaldehyde. The procedure is economical because small quantities of relatively inexpensive isotopes are used and it is at least as sensitive as silver staining in detecting proteins. A fourfold increase in the sensitivity of autoradiography over existing methods was obtained by performing autoradiography before processing the gel for fluorography. A spot in the electrophoretic gel that contains 17-28 ng of labeled protein is detectable. This corresponds to proteins present in serum at a concentration of 5-10 micrograms/ml. Even greater sensitivity can be achieved, at greater expense, by increasing the quantities of the radioisotopes in the labeling reaction. The particular value of the double label approach is that complex mixtures from two different sources are resolved together thus eliminating the possibility of differences arising from the resolving procedure itself. The procedure was applied to a mixture of serum and plasma from a single subject and a number of qualitative and quantitative differences were observed.

The effect of substrate and epidermal growth factor on human placental trophoblast cells in culture

Attempts were made to select for trophoblast cells in cultures of mixed cell populations derived from preterm (7 to 12 wk) or term human placentas. Epidermal growth factor added to cultures on solid or porous supports caused proliferation of epithelial-type cells to give a confluent monolayer but did not increase the expression of differentiated function. The presence or absence of placental basement membrane collagen as substrate made little apparent difference; however a porous basement membrane collagen support led to increased differentiated function. Initial production of human chorionic gonadotrophin was increased and after 4 wk in culture a substantial proportion of the cells exhibited alkaline phosphatase activity. Epidermal growth factor and a substrate of placental basement membrane collagen on a porous support favorably influence the growth and differentiation of human trophoblast cells in culture.

Intracellular binding proteins for retinol and retinoic acid in early and term human placentas

Specific binding of both [3H]retinol and [3H]retinoic acid was observed in the cytosol fraction from term placentas and specific binding of [3H]retinol but not [3H]retinoic acid was detected in the cytosol fraction from placentas of 8-12 week pregnancies. The elution volume of the bound radioactivity on Sephadex G-100 column chromatography was within the range expected for proteins of molecular weight 14 500, in agreement with the results of others for cellular retinol- and retinoic acid-binding proteins from other tissues. The role of these proteins in mediating the effects of vitamin A on growth and differentiation of the placenta and fetus has yet to be determined.

Proteins of human placental microvilli: II. Identification and topology of the plasma membrane proteins

We have investigated the location of proteins in the transverse plane of the plasma membrane of microvilli isolated from the syncytiotrophoblast layer of the human term placenta. Microvillous proteins were labelled with 125I under reaction conditions where those proteins exposed on the maternal-facing surface of the microvilli were most heavily labelled. The proteins were then solubilized and subjected to one- and two-dimensional electrophoresis followed by protein staining and autoradiography. More than 65 proteins, differing in molecular weight or isoelectric point or both, were identified, and these were classified into three groups: weakly, moderately heavily, and heavily labelled. The microvilli were in the form of intact vesicles that were correctly orientated ('right-side out'). Thus the extent of labelling of each protein could be used as an indication of the extent of its exposure on the maternal-facing surface of the microvilli. Human serum albumin was present on the surface of the isolated, washed microvilli, but was probably a contaminant originating from maternal blood.

Proteins of human placental microvilli: I. Cytoskeletal proteins

Microvilli isolated from the syncytiotrophoblast surface of the human term placenta were separated into two fractions, one of which contained microvilli lacking a visible cytoskeleton on electron microscopy. One- and two-dimensional electrophoresis showed that a number of proteins were present in reduced amounts in the fraction lacking a visible core structure. The possibility that these proteins were cytoskeletal components was investigated by further electrophoretic studies in conjunction with 125I labelling of proteins of intact and disrupted microvillous vesicles, digestion of external proteins with immobilized, insoluble trypsin, and selective solubilization of plasma membrane proteins by Triton X-100. From the results of these studies, eight proteins of molecular weights 103 000, 80 000, 70 000, 69 000, 43 000, 36 000, 25 000 and 18 000 were tentatively assigned to the cytoskeleton. The differences between our findings for the cytoskeletal proteins of human placental microvilli and the results reported by others for the well-studied cytoskeletal proteins of the intestinal microvilli of the rat are likely to reflect differences in structure and function of the microvilli from the two sources.

Anterior mediastinal mass and Graves' disease

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Abnormalities of serum and plasma components in patients with multiple sclerosis

Qualitative and quantitative abnormalities in protein and non-protein components of serum and plasma in patients with multiple sclerosis have been the subjects of numerous reports. In this review many of the more recent observations are documented and evaluated. It is concluded that at present the welter of information that has been gathered does not contribute in any major, coherent way to our understanding of the etiology or pathogenesis of the disorder. Several of the abnormalities that have been observed may be future candidates for biochemical markers for multiple sclerosis; at present none is sufficiently reliable, distinctive or easily performed to warrant the status of a useful diagnostic or prognostic test.

Human placental microvilli contain high-affinity binding sites for folate

Uptake of [3H]pteroylglutamic acid [( 3H]PteGlu) was studied in microvilli isolated from the syncytiotrophoblast of the human term placenta. The effect of changes in medium osmolality on the equilibrium uptake of [3H]PteGlu was negligible, which suggested that the observed uptake represented binding to proteins on or within the microvilli rather than translocation of the vitamin from the incubation medium to a free state in the intravesicular fluid. Equilibrium uptake experiments performed over a wide range of [3H]PteGlu concentrations disclosed a class of binding sites with an association constant of 0.3 nM-1 as well as a second class of sites with high capacity and low affinity. Binding of [3H]PteGlu at the high-affinity sites was inhibited by tetrahydrofolate and N5-methyltetrahydrofolate, but not by several other structural analogues. It is likely that the high-affinity binding sites are receptors for maternal plasma folate; however, their role in placental transport or storage of the vitamin was not delineated in these studies.

Squamous cell carcinoma of the eyelid masquerading as 'malignant' ophthalmopathy of Graves's disease

A patient with Graves's disease is described in whom the periorbital changes of severe ophthalmopathy and iatrogenic Cushing's syndrome delayed the diagnosis of a squamous cell carcinoma of the eyelid. It is suggested that the immunosuppressive therapy which the patient received may have enhanced the growth of a pre-existing malignancy.